1. Field of the Invention
The present invention relates to the field of producing protein polymers through self-assembly of monomeric polypeptide units and to various uses of the self-assembled protein polymers.
2. Description of the Prior Art
Nanotechnology is taking center stage in efforts to build the next generation of computational tools and medical devices. The ability to rearrange molecular structures will have a profound effect on how products are manufactured. However, one drawback to synthetic nanostructures constructed from materials such as carbon and silicon has been the difficulty in attaining self-assembly of such components.
Nanobiotechnology relates to the development and use of biomolecular structures for applications such as biochips, drug delivery, data storage and nanomachinery. Nature produces molecular machinery that outperforms anything mankind currently knows how to construct with conventional manufacturing technology.
One application for nanobiotechnology is targeted drug delivery. The major goal of targeted drug delivery is the local accumulation and increased bioavailibility of a therapeutic agent at its intended site of action, thereby reducing the drug dosage required to illicit the desired response. These sites of action include pathogenic bacteria and viruses, cancer cells, and areas of inflammation or other tissue damage. There are a variety of targeted drug delivery systems that are currently being developed and these include: liposomes, soluble polymer carriers, lipid and polymer gels, and various nanosuspensions (Torchilin, Drug Targeting. Eur. J. Pharmaceutical Sciences: v. 11, pp. S81-S91 (2000); Gerasimov, Boomer, Qualls, Thompson, Cytosolic drug delivery using pH- and light-sensitive liposomes, Adv. Drug Deliv. Reviews: v. 38, pp. 317-338 (1999); Hafez, Cullis, Roles of lipid polymorphism in intracellular delivery, Adv. Drug Deliv. Reviews: v. 47, pp. 139-148 (2001); Hashida, Akamatsu, Nishikawa, Fumiyoshi, Takakura, Design of polymeric prodrugs of prostaglandin E1 having galactose residue for hepatocyte targeting, J. Controlled Release: v. 62, pp. 253-262 (1999); Shah, Sadhale, Chilukuri, Cubic phase gels as drug delivery systems, Adv. Drug Deliv. Reviews: v. 47, pp.229-250 (2001); Müller, Jacobs, Kayser, Nanosuspensions as particulate drug formulations in therapy: Rationale for development and what we can expect for the future, Adv. Drug Delivery Reviews: v. 47, pp. 3-19 (2001)).
Targeted drug delivery systems that utilize encapsulation are attractive because 1) they require lower doses of therapeutic than non-targeted, even biodistribution approaches; 2) the therapeutic is less likely to cause unwanted side effects in healthy tissues because it remains concentrated, isolated, and therefore protected, until delivery; and 3) large numbers of therapeutic molecules can be delivered to a site of action using few targeting vectors attached to the encapsulation vessel.
One recent development in the area of nanotechnology employs eukaryotic microtube assemblies as a structural framework. Eukaryotic microtubules self-assemble into hollow rods and this property has made them attractive candidate structural components for a variety of nanotechnology applications (Jelinski, Biologically related aspects of nanoparticles, nanostructured materials, and nanodevices, In Nanostructure Science and Technology, A WTEC Panel Report prepared under the guidance of the Interagency Working Group on Nanoscience, Engineering and Technology (1999); Fritzsche, Kohler, Bohm, Unger, Wagner, Kirsch, Mertig, and Pompe, Wiring of metalized microtubules by electron beam-induced structuring, Nanotechnology: v. 10, pp. 331-335(1999)).
However, the use of microtubules presents numerous challenges, including the lability of microtubule subunit proteins, the requirement for GTP for microtubule assembly and the need for microtubule stabilizing drugs like taxol to prevent the depolymerization of the tubules below 37° C. or in the presence of calcium. In addition, a major drawback of eukaryotic microtubules is the inability to overexpress microtubule subunits in E. coli in a functional form and therefore microtubule protein must be isolated from a native source, most commonly bovine brain (Lewis, Tian, Cowan, The α- and β-tubulin folding pathways, Trends in Cell Biology: v. 7, pp. 479-484(1997); Shah, Xu, Vickers, Williams, Properties of microtubules assembled from mammalian tubulin synthesized in Escherichia coli, Biochemistry: v. 40, pp. 4844-4852 (2001); Williams and Lee, Preparation of Tubulin from Brain, Methods in Enzymology (Academic Press): v. 85 pt. B, pp. 376-385 (1982)).
In addition, substrates for delivery of biocatalysts for synthesis reactions are needed. Such substrates may be three-dimensional to provide more catalytic sites and, as a result, it may be advantageous to develop such substrates from self-assembling polymers. Also, three-dimensional polymeric structures may be useful for other applications such as separation processes or screening methods.
Accordingly, it is an objective of certain embodiments of the present invention to provide a method of making a protein polymer, which employs self-assembly.
It is an objective of certain embodiments of the present invention to form a nanoscale drug delivery vehicle for targeted drug delivery.
It is an objective of certain embodiments of the present invention to provide fibers made from a self-assembled protein polymer.
It is a still further objective of certain embodiments of the present invention to provide three-dimensional arrays made from a self-assembled protein polymer.
It is a still further objective of certain embodiments of the present invention to provide a medium for biocatalysts based on a self-assembled protein polymer.
These and other objects of the present invention will be apparent from the summary and detailed descriptions, which follow.